| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust gas cleaning catalyst capable of easily isolating sulfur adhering thereto and having a high NOx removal efficiency especially in excess oxygen region (lean region). SOLUTION: The exhaust cleaning catalyst comprises a first layer (1) containing a HC adsorbent, a second layer (2) containing NOx cleaning-up catalytic component on the first layer, and an alkali compound (3) with a crystal diameter of 250 Å and contained in the second layer (2) together with Rh, Pd, and Pt. The catalyst is produced by producing a slurry by mixing a powder of alumina carrying Rh, Pd, and Pt with an aqueous solution of a water soluble salt of alkali metals or alkali earth metals, adjusting the pH at 7.0 to 12.0, adjusting the slurry particle diameter to be 0.1 to 5 μm, depositing it on the first layer, drying at a temp. of 100-300 deg.C, and firing at a temp. of 400-700 deg.C. |
